The best synthetic gasketing materials have plenty of company. They’re originally manufactured as single-solution rubbers and plastics, but then the chemist gets into a fine-tuning “groove.” Before long, different variants are keeping the original product company. And so it is with Viton “A,” a fluoropolymer-based synthetic elastomer. A core member of the main Viton product group, this synthetic rubber seems like it’s found a match-made-in-heaven relationship with the automotive industry.

Resists Lubricant Attack 

Oily streams course all throughout a car’s internal combustion engine. Viton “A” is the go-to gasketing product here because the material incorporates a potent lubricant resistance feature. Attacked by the many oils and greases that are carried in automobile conduits, the gaskets won’t deteriorate when they’re in contact with these potentially aggressive fluids.

A Hydrocarbon Hero 

Next up, the petrol, gasoline for our American cousins, used to fuel cars is based on a complex soup of combustible hydrocarbons. Like the lubricants in the engine, that fuel was created when it was processed in some faraway oil refinery. At any rate, hydrocarbons are known for their gasket-abusing aptitudes. Well, thanks to a set of qualities that clearly targets these refined fluids, Viton “A” gaskets tolerate hydrocarbons very well. Imagine a lesser rubber seal in there, one that was deteriorating because of the fuels solvent-like features. Fuel leaks cannot be allowed, which is why this fluoropolymer-based synthetic is seen as the de facto solution in car fuel systems.

Enduring the Combustion Cycle 

A mistreated car issues a bang and pulls off to the side of the road. Another car is suffering, too. It’s still running, but a strangely coloured smoke trail is pouring from the exhaust pipe. Everyone knows great internal energies are being consumed everytime a car engine starts. As the car ages or gets prematurely aged by a speed-enthusiast, its gaskets become brittle. Happily, Viton “A” is a robust elastomeric product. It withstands the high temperatures and pressure differentials that spike when engines are pushed to their limits. Frankly, the gaskets in the cylinder heads and engine block should never be perceived as a machine weak link, and A-type Viton exists to reinforce that mandate.

Emissions regulations are now incredibly stringent in the automotive sector. Furthermore, there are many, many fuel variants coursing below petrol station islands. They have special additives and exotic engine cleaners. Even if a tough gasket was specifically designed to contain regular petrol streams, there’s no way the same could be said when these exotic mixes are used. Well, thanks again to Viton “A,” whatever the fuel or oil formulation, a fluoroelastomer-gasketed vehicle will continue performing at its best, with no leaks.

Clear differences divide gaskets and conventional washers. The former item uses strong materials to mechanically seal flanges. As for the latter item, washers are typically used to spread fastener loads and to counteract vibrations. That’s good to know, except sealing washers, the subject of this post, don’t quite fit into that latter category. No, this washer family shares gasketing features, but they’re not gaskets.

Reviewing Gasket Roles 

A gasket is carefully placed around an opening of some type. Whether the perimeter of that opening is in an engine block or the flanges of a pressurized pipe, the seal fulfils its role as a fluid constraining device. The loop of circular or shaped material can be manufactured from some durable elastomeric material, from metal, or even from a combination of the two, but its role is still very clear. Compressive loads bear down on the seal, the material endures unimaginable fluid pressures, and that’s the job done. Sealing washers are different, even though they also possess fluid-stoppering talent.

Multipurpose Sealing Washers 

Here’s a washer family that also uses a malleable surface to constrain fluids, but that’s just one of the several features we discover when using a sealing washer. In truth, they’re composites. On top of the washer, a strong metal backing spreads fastener loads. Underneath that hardened ring, a second ring, perhaps made of EPDM (Ethylene Propylene Diene Monomer) or Silicone, delivers face-sealing strength. They’re structural accessories, which means they’re capable of anchoring a surface while they also seal that same plated object. Beyond those two key product characteristics, sealing washers also use their synthetic rubber faces to attenuate vibrations.

Some Design Differences 

Gaskets are clearly designed to endure high fluid pressures, plus they’re known to assume countless geometrically complex profiles. Tough fibres and metals and synthetic rubbers are processed into layered rings, and those rings are compressed between pipe flanges. That’s a standard gasket application, but then there are engine gaskets, hydraulic seals, and more. Sealing washers stick to a tried-and-trusted circular profile. However, they’re partially exposed, so additional design parameters need attention. The alloy ring obviously must be tough and corrosion resistant, but what about the vibration and fluid stoppering rubber? Well, UV resistance is desirable here, as is ozone resistance and a general aptitude for staying strong when weather extremes push the sealing faces hard.

Gaskets differ from sealing washers in several ways. It’s important to know those differences, to know which product is bound for which application. Stronger by nature, gaskets seal pipe flanges, mechanical housings, and more. They’re strong and durable, but that’s their sole purpose. Sealing washers are fastener accessories, plus they provide fluid sealing strength and a feature that addresses mechanical vibrations.

Vulcanized materials are exposed to high-temperatures and special additives. Essentially, these curatives function as cellulose binding agents. In gasket processing, the process adds tensile strength to the hard, durable rings, plus mechanical resistance. The treated gaskets endure when strong compressive forces are applied, and they’re equipped to deal with material damaging abrasive actions. Let’s look at some common usages for these vulcanized products.

Defining Material Characteristics 

Take a closer look at a table full of vulcanized rubber gaskets. Some are thicker than others, so they’re rated to handle compressive flange stress. Also, on the same desk, there are coloured and graded vulcanized materials. In plain terms, the source fibre varies from one grade to the next. For instance, cotton pulp is a common fibre type, as is wood pulp and other cellulose-rich substances. Durable by nature, the gaskets are pressed, calendered, and dried until they suit a nominated application.

Electrically Graded Seals 

Known as “fish paper” by industry insiders, this thin vulcanized material is dimensionally stable. Proven as an extremely flat gasketing solution, the die cut substance is commonly used as an arcing shield and dielectric. This time around, instead of pressurized fluids, the application base evokes images of electrical substations, of high potential differences and dangerous electrical charges. Cut to shape, the vulcanized fibre forms the insulation on high voltage transformer coils and grid distribution insulation.

Commercial Grade Gaskets 

Made almost entirely of crushed cellulose, the sheet material arrives laminated in plastic. The homogenized material won’t separate, not even in water, and it’s a natural fit for the petrochemical sector. Lacking chemical resins, the gaskets are hard and chemically pure. Taking those two features into account, the seals slot into place on automobile fuel and lubricating systems, solvent storage facilities, and petrochemical processing plants. For further material strength, the fibres can be blended with cork granules.

Dynamic Applications 

Motor vehicle engines kick out great quantities of mechanical energy. Cylinders rise and fall, crankshafts spin, and drive trains engage wheels. In the cylinder heads, die cut vulcanized fibre gaskets contain the lubricating oil and intense kinetic forces. Back at the electrical transformer, similar energies are in motion. This time around, however, its electrical power, not kinetic energy, that’s testing the sealing strength of the gasket. After all, the cooling medium inside that transformer is oil, a fluid that would compromise most other electrical dielectrics and insulators.

Employed heavily in the automotive and electrical industry, vulcanized fibre gaskets are also used as high-strength petrochemical seals and machine cylinder gaskets. Expect to see them in their sealed plastic bags as red rings, although they also come in several other colours.

Caustic chemicals cause strong materials to smoke and sizzle. Even vulnerable metals experience fatigue and corrosion when a particularly concentrated alkali or acid attacks. If corrosive chemicals can eat durable metals, what chance does a gasket stand of enduring such an attack? To answer that question, read on and learn about the specialized sealing materials that are capable of enduring these aggressive chemical attacks. Let’s begin with sulphuric acid.

Modified PTFE 

Polytetrafluoroethylene is known as Teflon by most. It’s a synthetic polymer that’s equipped with a good-to-moderate acid and alkali resistance feature. Modified PTFE adds exotic fillers to the fluoropolymer backbone so that the soft gasketing material gains mechanical strength.

Ethylene Propylene Diene Monomer 

Although EPDM is vulnerable to oil-based fluids, it’s a good candidate for a chemical processing system that’s loaded with salts, acids, and alkalis. For that reason, an engineer clearly wouldn’t select this material as a petrochemical sealer, but the selection process would quickly skip to EPDM if the chemical base was an aggressive chemical. Incidentally, PTFE envelopes are known to further reinforce the capabilities of this gasket material.

Flexible Graphite 

This neutral element doesn’t react to the presence of strong chemicals. Instead, the exfoliated flakes withstand high pressures, temperature extremes, and caustic chemical loads. However, graphite is a soft material, which means it won’t perform well when large compressive forces are applied. To solve this issue, steel inserts or wires are added to the carbon base.

Adopting Metal Gaskets 

When polymers and fibres don’t work, metal gaskets take up the slack. However, there are countless options here, and some metals will react unfavourably when they’re attacked by a specific chemical. For example, copper and brass are both superior choices, but they will fail if the liquid stream contains an oxidizing agent. Steel is another option, but some ferrous-heavy gaskets are known to corrode when super-heated oxidizing fluids are at hand. Select an alloy that won’t corrode or harden when a selected chemical base receives a heat-induced kick.

Then there are the composites, the gaskets that mix-and-match these different materials. EPDM is a logical choice as a harsh chemical seal, but the ring of material works better when it’s covered in a PTFE envelope. Certain rubbers are moderate chemical resistors, but they gain strength when they’re bound with aramid fibre. Likewise, carbon flakes are mechanically soft but chemically inert. Just add metal to the flexible graphite to equip the gasket with strength. Glass-reinforced Teflon or metal, alloy or metal-reinforced polymer, the materials all defy the oxidizing effects of strong chemicals. But remember, this feature can only be demonstrated if the chemical stream is known.

This gasket family is commonly referred to under its truncated label, CNAF. In its entirety, Compressed Non-Asbestos Fibre materials are exactly that, a gasket type that doesn’t rely on an asbestos base. However, the easily classifiable materials list ends right there, for this is an umbrella term. Many different fibre types and binder groups occupy the CNAF category, and they’re all gifted with their own unique sealing features.

The Principal Material-Defining Factor 

Straight to the point, Compressed Non-Asbestos Fibre gaskets are best-suited for extreme processing conditions. If there are hydrocarbons and oils in the vicinity, or there are solvents and caustic chemicals around, then sheets of CNAF can be cut to fit while they guarantee a fatigue-free seal. Imagine a 0.25 mm thick product functioning as an acid pipe seal. Alternatively, if temperature extremes and high pressures are part of the application’s daily runnings, then an upscaled 3 mm thick sheet will do the job.

Table Selection Methods 

The CNAF category is organized tables. The categorized list, framed in a tabulated form, incorporates glass and aramid fibres, nitrile and other synthetic rubber binders, and all kinds of metallic inserts. As a finger runs down the listed materials, application attributes come to mind. There’s the need for a maximum processing temperature, a matching need for outstanding performance, and a reserved area of the rows and columns that states which hazards are best handled. Typically, the gaskets will maintain their features when solvents and petrochemical oils are the source flow medium. However, this general purpose build adapts to include fibre types that hold strong when steam, refrigerants, and specific chemicals are flowing.

The Multiplicity Factor 

Imagine all of the active chemicals and fluid conditions that dominate countless industrial and commercial applications. A single gasket type will likely satisfy the stringent codes that are enforced by one or two of these sites, but there’s no way they’ll fit every process. That’s the real power of CNAF, the group’s nearly unlimited number of gasketing options. Glass and aramid fibres dominate, but then there are carbon fibres, Kevlar and several other mineral bases. The key, therefore, is to stop this strength from being perceived as a weakness.

The best way to take advantage of CNAF is to be familiar with the material/features tables. Begin by learning about the various mineral bases, refine that approach by assessing mechanical strength. That latter feature could be woven into the fibre or be incorporated as a mild steel ring. Finally, select a binder, a synthetic rubber, that won’t be the weak link in this compounded non-asbestos gasketing solution.